Duplex translating-circuits



J. R. CARSON.

DUPLEX TRANSLATING CIRCUITS.

APPLICATION FILED MAR.26. 1917. RENEWED MAY 27. 1919.

153435308. Patented June 15, 1920.

4 i I I I I I ,fie 19120 1 Fz' tar INVENTOR ATTORNEY stares JOHN R.CARSON, 0F MONTCLAIR, NEW JERSEY, ASSIGNOR TO AMERICAN TELEPHONE ANDTELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

DUPLEX TRANSLATING-CIRCUITS.

raiasos.

Specification of Letters Patent.

Patented June 15, 1920.

Original applicationfiled September 5, 1916, Serial Ito. 118,573.Divided and this application filed March k 26, 1917, Serial No. 157,414.Renewed May 27, 1919. Serial No. 300,180.

To all whoin it may concern:

siding at Montclair, in the county of Essex and State of New Jersey,have invented certain Improvements in Duplex Translating-Circuits, ofwhich theafollowing is a specification.

I The invention of this application, which is a division of applicationSerial No. 118,- 573, filed September 5th, 1916, relates to signalingcircuits and has for its general object the provision of a duplextranslating system which is capable of a wide range of utility, andwhich shall exhibit a high degree of efficiency in thevariousapplications of which it is capable.

In its general embodiment the invention comprises a duplex translatingstructure having a pair of input and a pair of output circuits, the pairof input circuits being symmetrically associated with one source ofcurrent variation, and oppositely associated with a second source, theoutput circuits being differential with respect to one or: receivingcircuit and cumula- 1 spect to another outgoing cirthe first mentionedsource protue of its symmetrical conneci t1 e fluctuations of the samephase in'the'two input circuits, while the second'mentioned source, byvirtue of the I .fact that the input circuits are oppositely associatedtherewith, produces potential fluctuations of opposing phase in saidinput circuits. This statement is made to define the significanceattached to symmetrical and opposite connections in this specification.

Thus in general there may be four main elements comprising two sourcesand two receiving circuits which may be variously related to thetranslating device proper. Additional results may be produced by theomission of one or more of the four main elements, with correspondingchanges in the connections of the remaining elements. The form oftranslating device used may preferably be of the thermionic vacuum tubetype,

carrier wave signaling in which the necessity for high frequency tuningand selectivity is eliminated.

The invention will-ebe more fully under stood by reference to the.drawing in which Figures 1, 2, 3 and L illustrate four modifications ofa selective receiving system for multiplex carrier currents.

Referring now to F igul, a pair of three element thermionic tubes,having filaments 1, 2, grids 3, 4, and plates 5, 6, are provided, thefilaments being heated by a battery 7. The tubes are preferably similarand equal in their structure and characteristic, and are equivalent toand may be replaced as illustrated in Fig. 4 by a single duplex tubesuch as is shown in the patent of E. H. Colpitts, 1,128,292, February16th, 1915. The input circuits of the tubes are arranged in parallelwith respect to the secondary of a transformer 68 in the commonconductor of the two input circuits.

'The output circuits are also connected in a circuit 62 which terminatesin the primary 63 of a transformer 64, having two secondary windings .65and 66, one included in each of the input circuits of the repeater.

A local source of high frequencyis sup-- plied by a homodyne orheterodyne enerator 67 which is coupled through transormer 68 to thecommon conductor of the two input circuits. Itwill be understood that aheterodyne generator is a source of alternating current energy of afrequency differing from that of the incoming carrier wave by a pre-assined frequency preferably "Within the limits of audition, while ahomodyne generator is a source of energy of a frequency'identical withthat'of, the" incoming carrier wave. Theformer is employed whenunmodulated carrier waves are transmitted, while the latter ispreferably employed when the carrier wave is modu- \certain limit, butpermit the passage with-" lated as in carrier wave telephony. In eachoutput circuit is inserted a primary wind-' ing of a transformer 69, thewinding in circuit with plate 5 being designated and that in circuitwith plate 6 being designated 71. The secondary 72 of the transformer'isconnected to a circuit 73 leading through a low frequency filter (notshown) to a receiving instrument. -The filter to be used is of a wellknown type of broad band filter which will suppress all frequenciesabove a out attenuation of all frequencies below this limit, which fortelephonic purposes might be fixed at 2,500 cycles. This typeof filteris disclosed and fully described in U. S. Patent of G. .A. Campbell, No.1,227,113, issued May 22, 1917.

The operation of the apparatus will be understood from the followingconsiderations:

It has been pointed out in a U. S. patent issued to Maurice LeBlanc, No.857,079 of June 18, 1907, that when a plurality of carrier currents ofdifferent frequencies, each modulated by voice'currents are sent out on;a line, and at a receiving station afrequency equal to that of one ofthe carriers is provided, this frequency will interact with themodulated carrier, current having the same period, with the result thata suitable receiving instrument will respond to the low frequency voicecurrents by which that particular carrier is modulated, while carriershaving a different frequency will be without effect. A.- fulltheoretical discussion of the principles involved is given inthe abovepatent and need not here be repeated, it being sufficient to point outthat if a plurality of carrier waves havingfrequencies f f f be sent outon the line, each modulated at audio frequency p, and further if atthe'receiving station a homo dyne frequency f equal to the frequency ofone of the carrier waves be allowed to interact therewith, a pluralityof frequencies will result in the output circuits of the repeaterstructure of Fig. 6 as follows:

(f1+fk+2 f1+fk1I (f1f1 +1 (flfk p) (Aura; (am 52 2112 acre. Assumingthat the homodyne frequency f is equal to frequency f,,, the last fourfrequencies reduce to (2f +p),' (2f p), p and p. If the carrierfrequencies differ from each other by an amount greater than 279 it willbe clear that all of the frequencies above set forth except 3? and- 0will be greater than 10. Hence a filter .in the outgoing circuit whichsuppresses all frequencies above 37 will suppress everything except theaudio frequency by which carrier frequency 7",. was modulated. 'Thesignals by which other carriers were modulated w ll not be receivedbecause the resultdyne frequency to the common conductor .-1,34 spos antfrequencies due to their interaction with the carrier frequency and thehomodyne frequency will be greater than 10. It will now be apparent thatby applying the homo-' 70 of the input circuits of Fig. l'throughtransformer 68, so that this frequency interacts with the severalincoming carrier frequencies modulated by low frequency signals, thevarious resultant frequencies 75 above set forth will appear in theoutput A circuits of the repeater and be impressed on outgoing circuit73 through transformer 69, the filter acting to suppress everythingexcept the voice currents which modulated the carrier current having thesame frequency as the homodyne generator. The same effect will beproduced if the incoming car- -rier currents are impressed upon thetranstheincoming line, the energy from the generator does not react upontheline and cause a tone in other receiving devices upon the same line.A further advantage attaching to the use of duplex translatingarrangements resides in the fact that distortion' of the incoming signalwhich is always and inherently caused by ordinary detectors issubstantially eliminated by the combination of the duplex detector witha 0 local homodyne generator. Consequently the utility of the duplexdetector is not limited to its-use in combination with afilter nor is itlimited to use in a multiplex system. t

A slight modification is shown in Fig. 2 in which the incoming carriercurrents are impressed upon the input circuits of the duplex detector bya conductive connection instead of by an inductive connection such asshown in Fig. 1. The two sides of the incoming line 74 are directlyconnected to I the grids 3 and 4, and are bridged by'substantially equalresistances 75 and 76, to the mid-point of which the common conductor'lfi of the input circuits of the detector is connected, the homodynecurrents being applied jus t as in Fig. 1. The operationis similar'tothat already described in connection with Fig. 1. v In Fig. 3 analternative arrangement is shown in whichthe incoming line 77 isdirectly connected in the common conductor of the two input circuits ofthe repeater, while the homodyne currents from gener- -125 ator 67 areapplied through a transformer 78, having secondary windings 80 and 81,one in each of the input circuits. The operation of this circuit issimilar to that of Figs.

rangements of Figs' 1, 2 and 3 are essentially equivalent and that theparticular connections are immaterial although preferably one of the twosources of potential variations should be applied symmetrically orcumulatively and the other oppositely to the two input circuits and thereceiving circuit 73 should be differently coupledto the two outputcircuits. Theinvention is not limited to such an arrangement, however.

It will be seen that by this invention a duplex translating system hasbeen devised which is both simple and efficient and which is capable ofa large number of applications to produce widely varying results. Whilethe invention has been illustrated as embodied in a limited number offorms it will be understood that the embodiment may be widely variedwithout departing from the scope of the appended claims.

What is claimed is:

1. A receiving apparatus for carrier wave signaling systems comprising apair of translating devices having input and output circuits, a circuitfor the reception of high frequenc signals, a second circuit containinga loca source of high frequency energy, one of said circuits beingsymmetrically associated with said input circuits, and the other beingoppositely associated-with said input circuits, and a receiving circuitdifferentially associated with said output circuits.

2. A receiving apparatus for carrier wave signaling systems comprising aduplex detector arrangement having divided input and divided outputcircuits, a circuit for the reception of high frequency signals, asecond circuit containing a local source of high frequency energy, oneof said circuits being symmetrically associated with said input circuitsand the other being oppositely associated with said input circuits, anda receiving circuit differentially associated with said output circuits.I

3. A receiving apparatus for carrier wave signaling systems comprising apair of transv lating devices having input and output circuits, acircuit for the reception of high frequency signals, a second circuitcontaining a local source of high frequency energy, one of said circuitsbeing symmetrically associated with said input circuits and the otherbeing oppositely associated with said input circuits, a receivingcircuit differentially associated with said output circuits, and afilter in said receiving circuit.

4. A receiving apparatus for carrier wave signaling systems comprising aduplex detector arrangement having divided inputand divided outputcircuits, a circuit for the reception of high frequency signals, asecond circuit containing a local source of high frequency energy, oneof said circuits being symmetrlcally associated with said input circuitsand the other being oppositely as- I sociated with said input circuits,a receiving circuit differentially associated with said output circuitsand a filter in said receiving circuit. I

5. In a multiplex carrier wave transmission system, a receiving s stemcomprising a pair of translating devlces having input and outputcircuits, a circuit for the reception' of signal waves, a second circuitcontaining a source of energy of frequency substantially equal to thatof one of the carrier waves, one of said circuits being symmetricallyassociated with said input circuits and the other being oppositelyassociated with said input circuits, a receiving circuit differentiallyassociated with said output circuits and a filter in said receivingcircuit. I

6. In a multiplex carrier wave signaling system, a receiving systemcomprising a duplex translating arrangement having idivided input anddivided output circuits, a circuit for the reception of signal waves, a

se'cond circuit containing a source of energy of frequency substantiallyequal to that of one of the carrier waves, one of said circuits beingsymmetrically associated with said input circuits and the other of saidcircuits being oppositely associated with said input circuits, areceiving circuit differentially associated with said output circuitsand a filter in said receivingcircuit.

7 A receiving apparatus comprising a pair of translating devices, acircuit upon which carrier currents of different frequencies areimpressed, said last named circuit being associated with the translatingdevices, a source of local oscillations of a period substantially equalto that of one of the carrier currents associated with said repeatercircuits, and an dutgoing circuit provided with a low frequency filterassociated with source will be effective in the outgoing circuit.

8. In a receiving apparatus, a pair of re- 1 peater, circuits comprisinga common conductor and also individual sections, a cir cuit upon whichcarrier currents of. different frequencies are impressed, said lastnamed circuit being serially associated with the individual conductorsof the repeater circuits, a source of local oscillations of a periodsubstantially equal to that of one of the carrier currents associatedwith the common conductor-of the repeater clrcuits, and an outgolngc1rcu1t provlded w1th a low fre-' quency filter associated with saidrepeater circuits, whereby only the low frequency signals impressed uponthe carrier currents of the frequency of the local source will beeffective in the outgoing circuit.

9. In a receiving apparatus, a duplex repeater arrangement comprisin apair of input and a pair of output circults, each pair having a commonconductor, a circuit upon which carrier currents of difierentfrequencies are impressed, said last named circuit being seriallyassociated with the two' input circuits, .a' source of localoscillations of a frequency substantially equal to that of one of thecarrier currents associated with the common conductor of said inputcircuits, and an outgoing circuit provided with a low frequency filter,differentially associated with the output circuits, whereby only thelowfrequency signals impressed'upon the carrier currents of thefrequency of the local source will be effective in the outgoing circuit.

10. In a receiving apparatus, a pair of repeater circuits comprising acommon conductor and also individual sections, means for applyingreceivedoscillations to said repeater circuits in such manner as toreact serially upon the individual sections thereof, a source of localoscillations of a fre quency slightly differing from that (if thereceived oscillations, means associating the local source with thecommon conductor of the repeater circuits, and an outgoingciroscillations and another of said independent circuits comprising areceiving circuit, one

of said independent circuits being associated with said common path.

12. A translating apparatus comprising a duplex translating arrangementincluding a common path and individual paths, a plurality of independentcircuits, one of said independent circuits comprising a source ofmodulated high frequency oscillations, another of said independentcircuits comprising a source of unmodulated high frequency oscillationsand another of said independ ent circuits comprising a receivingcircuit,

I one of said independent circuits being associated with said commonpath, and the others of said independent circuits being as sociatedwith. said individual paths.

13. .A translating apparatus comprising a du lex translatingarrangement, parallel circults for said translating arrangementincluding a common path' and individual" paths, conductive evacuatedgaps in said individual paths, a source of unmodulated high frequencyoscillations and a source of modulatQd high frequency variationsassociated with said circuits, one of said sources being associated withsaid circuits through said common path, and the other of said sourcesbeing associated with said circuits through said individual paths. 1 15.A translating apparatus comprising a duplex translating arrangement,parallel circuits for said translating arrangement including a commonpath and individual paths, conductive evacuated gaps in said individualpaths, a plurality of independent circuits comprising a source'ofunmodulated high frequency oscillations, a source of modulated highfrequency oscillations and a receiving circuit," one of said independentcircuits being associated with said parallel circuits through saidcommon path.

16. A translating apparatus comprising a duplex translating arrangement,parallel circuits for said translating arrangement including a commonpath and individual paths, conductive evacuated gaps in said individualpaths, a plurality of independent circuits comprising a source ofunmodulated high frequency oscillations, a source of modulated highfrequency oscillations and a receiving circuit, one of said independentcircuits being associated with said parallel circuits through saidcommon path, and the others of said independent circuits beingassociated with said parallel circuits through said individual paths.

17. A receiving apparatus for carrier wave signaling systems comprisinga duplex translating arrangement including a common path and individualpaths, a circuit'for the reception of high frequency signals, a secondcircuit including a local source of high frequency energy, one of saidcircuits being associated with said common path and the other of said-circuits being associated with said. individual paths, an outgoingcircuit associated with said translating arrangement, and a filter insaid outgoing circuit.

18. A receiving apparatus for carrier wave signaling systems comprisinga detecting arrangement for translating highfrequency receivedoscillations into low frequency signaling current, a circuit to supplyhigh frequency r'eceived oscillations to said detecting arrangement, anda circuit for supplying local high freqnencenergy name to thisspecification,.'in the presence to said detecting arrangement, saiCiICUJI'S of two subscribing witnesses; this 15th day being soassociated with said detecting arof March, 1917. rangement that energyfrom said last men- JOHN R. CARSON. 5 tioned circuit will not react uponsaid first Witnesses:

mentioned circuit. RALPH W. WOLF,

In testimony whereof I have signed my FREDK S. ROBINSON.

